The present invention relates to solid particles containing calcium peroxide, to a process for their manufacture, and to their use in the treatment of water.
Calcium peroxide constitutes a very valuable source of active oxygen. In the form of an anhydrous solid, the product decomposes only very slightly under the action of heat. In an aqueous medium, on the other hand, it decomposes and liberates active oxygen. When the product is in powder form, this hydrolysis is particularly rapid at pH values below 10, so that the product becomes inactive just a few minutes after it has been brought into contact with the aqueous medium. Thus, the product cannot be suitable of the oxygenation of water when a long-term action is essential. Furthermore, granulation of the product does not reduce the hydrolysis rate sufficiently to permit its use in the treatment of water.
It is known to use uncoated particles of calcium peroxide in fish culture to oxygenate breeding ponds in order to aid the growth of vegetable plankton, as disclosed in Japanese Publication No. 27,799/74. It is also known to "encapsulate" calcium peroxide by means of liquid or pastry compounds in order to obtain an additive useful in the baking of bread, as disclosed in U.S. Pat. No. 3,666,486. The coating agent is heat dispersible at a temperature of less than 50.degree. C. and disappears, so that the calcium peroxide is liberated, when the bread dough is worked.